1. Field of the Invention
The invention relates to an electric power steering apparatus.
2. Description of Related Art
Japanese Patent Application Publication No. 2004-10024 (JP-A-2004-10024) describes an electric power steering apparatus (EPS) that modifies steering angles of steered wheels by driving two motors to rotate. The EPS described in JP-A-2004-10024 controls a first motor and a second motor independently using a first drive circuit and a first control device, and a second drive circuit and a second control device, respectively. In other words, the steering angles of the steered wheels are modified by controlling the motors of two systems independently.
In the EPS described in JP-A-2004-10024, however, although the respective motors, drive circuits, and control devices of the two systems are controlled independently, the two motors must be driven using appropriate synchronization control in order to modify the steering angles of the steered wheels. To perform this synchronization control, the motors must be controlled while monitoring control timings and operating conditions of the first control device and second control device. When both control devices are monitored, a calculation load of one of the first control device and the second control device increases. When the calculation load increases, appropriate synchronization control for the vehicle condition cannot be performed, and therefore a tracking delay may occur, leading to a reduction in steering responsiveness.